The present invention relates to the alignment of a semiconductor on a ceramic carrier to a base substrate, and more specifically to an apparatus that securely grips a semiconductor on a ceramic carrier being bonded to a ceramic base substrate.
The process of manufacturing semiconductors is well established and involves several stages, one of which is a bonding process. The bonding process involves the submicron alignment of a semiconductor ceramic carrier on a ceramic substrate. The submicron alignment of the ceramic components can be accomplished with relative case employing micromanipulator stages to provide controlled motion; however at present, difficulties lie with the ability to fix and then release these ceramic components without causing a shift in positioning.
These devices must be rigidly held in place for the duration of the bonding process to prevent misalignment due to shrinkage of the adhesive used to bond the carrier to the substrate. The gripping device therefore must be robust enough to apply sufficient force so as to overcome any adhesive shrinkage forces.
Robust high force grippers, typically in the form of mechanical jaws such as pliers or tweezers, that can provide the necessary high gripping force, often cannot be disengaged without transferring some of the disengagement force to the carrier resulting in unwanted movement.
Gentle disengagement grippers, typically in the form of a vacuum inducing gripping apparatus such as suction cups, that can minimize unwanted movement during disengagement provide a relatively low gripping force.
For the foregoing reasons, there is a need for a rigid non-slip gripper that also providers a gentle release.
The present invention is directed to a gripping apparatus that satisfies this need. The apparatus is a microgripper comprised of at least two grippers having angled gripping faces lined with an abrasive material. The grippers are configured in opposing pairs above the horizontal plane with the top edges of their angled gripping faces oriented closest to each other and the bottom edges oriented furthest from each other. The grippers are separated to the width required to engage the upper edges of a carrier substrate between the top and bottom edges of the angled gripping faces whereby a grip is provided, maintaining consistent contact between the carrier substrate and the base substrate.
In one aspect of the present invention the grippers are spring mounted to transfer by deflection of the springs, the desired downward force. The spring mounting comprises a plurality of parallel pairs of cantilevered flat springs attached to a support structure forming a gripper assembly. The parallel spring pairs are separated by spacers thereby maintaining the gripper assembly in a parallelogram configuration so as to allow the grippers to move vertically while remaining parallel with the support structure and providing self-adjustment to variations in carrier substrate thickness and angle.
In another aspect of the present invention the abrasive lining of the grippers consist of a soft pad with an embedded crystalline material, typically diamonds. In a related aspect, the grippers have a small triangular protrusion left on the angled gripping face to aid in positioning these abrasive pads.
The practical range of the angle of the gripping faces is from about 30xc2x0 to about 60xc2x0, through an angle of about 50xc2x0 is preferred for semiconductor on ceramic substrates.
The gripper assembly is typically detachably affixed to a micromanipulator to provide controlled motion through X, Y, Z and rotation axes to facilitate alignment by translation and rotation of the carrier substrate on the upper surface of the base substrate.
Once the bonding process has been completed, the grippers are disengaged vertically by raising the gripper assembly through the Z axis utilizing the micromanipulator stages, following the same path as engagement but in the opposite direction thereby providing a gentle release.
This apparatus requires a lower skilled operator, a shorter training period, and produces a reduction in alignment time. All of these factors result in significant cost savings.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.